Skeletal dysplasias are a diverse and heterogeneous group of hereditary disorders characterized by malformations of bone and cartilage. These conditions affect development patterns in bones of growing children, and the clinical severity ranges from mild short stature to highly disfiguring, and even to lethal forms. Their treatment is very challenging, typically with no or limited success. This proposal is designed to explore the use of gene- and stem cell-based approaches to influence bone development in growth plate disorders characterized by aberrant constitutive cellular signaling in the growth plate chondrocytes. These biotherapeutic technologies offer the unique opportunity to manipulate and influence the cells in the developing growth plate, and if successfully applied, may functionally rescue bone growth and restore normal skeletal development. In this study, we will work to gain fundamental knowledge necessary for the rational design of a therapy for achondroplasia and Noonan syndrome. In attempting to address skeletal dysplasias, we have chosen to focus on these diseases because they are caused by gain-of-function point mutations affecting intracellular signaling in growth plate chondrocytes, and there exists transgenic mouse models containing mutations identical to that found in affected patients. The following specific aims will be addressed: Aim 1- To determine the biological effects of systemic gene delivery and overexpression of sFGFR3 in Fgfr3ach/+ mice. Aim 2- To determine if overexpression of sFGFR3 or inhibition of SHP2 expression can restore growth in bones from Ptpn11D61G/+ mice in an organ culture system. Aim 3- To determine the capacity of exogenous stem cells to influence the biology of diseased growth plate in vivo. The fellowship will contribute to the reintegration of Dr. Gouze, an expert in gene and stem cell therapies for musculoskeletal disorders, in the INSERM unit of Pr. Salles, an expert in pediatric endocrinology and growth disorders